Pushing machine moveable on rail for operating into the slag hole of steel smelting electric furnaces

ABSTRACT

A pushing machine is described, which is capable of running to opposite directions, upon remote control, along a length of rail provided in front of the mouth or slag hole of an electric furnace (10) for the smelting of iron products. It shows, at the end of an arm (5, 5a) telescopically extensible and preferably pivoting to be able to swing also in the vertical plane, a head or front shield (6) mounted on a frame (1) which can be anchored to the ground and is slidable on rails by means of wheels (2, 2&#39; . . . ), at least two of which are driving wheels. Said shield (6), having a size slightly smaller than the slag hole, has the function of keeping the scrap at the inside of the furnace during the charging operation and keeping the threshold free of the slag without any operator&#39;s intervention.

FIELD OF THE INVENTION

The present invention relates to a pushing machine movable on rail,adapted to operate into the slag hole of electric furnaces for smeltingof steel or iron products in general, to be remotely controlled.

BACKGROUND OF THE INVENTION

It is known that the electric furnaces for smelting of iron based scrapsbeing directly discharged from the top have a front opening, also called"slag hole" whose threshold or lower step forms the so-called "dam"suitable to keep the molten bath within the furnace and to be overflownby the slag only, which then is drained at an underlying level through atrap provided on the floor immediately at the outside of the slag hole.The latter also provides the passage for the oxygen lance through whichoxygen gas is blown at very high speed directly into the melting zonefor refining the melt.

Also some important inconveniences are known, in connection said slaghole and with the presence of mainly deriving from the top charge of thescrap, which causes the obstruction, at least partial, of the so-called"slag runner" which connects the outer mouth of the hole with the moltenbath and must remain unobstructed, in particular to allow the oxygenlance without obstacles.

On the other hand it is also known that usually it is necessary to awaitthat a cast is over to carry out, before the subsequent one begins, theso-called operation of "slag hole cleaning", in other words removing theslag, now cooled, that has deposited on the threshold of said hole, aswell as remaking the "dam". Of course this involves longer standstilltimes between one cast and another, with consequent reduction of theproduction capacity, since it is impossible to carry out theseoperations by hand with the electrodes being fed, near high temperaturesand with the operators under the danger of being hit by sparks or jetsof molten metal. Not only, but the removal of eventually cooled, solidslag, forming an integral block with the underlying step of refractorymaterial (usually dolomite), resulted in a substantial demolition of thestep itself or "dam" and its remaking, with an additional extension ofthe plant standstill time.

It has been thought of over coming these inconveniences by using a powershovel that can hold the batch of charged scrap at the inside of thefurnace while keeping the slag runner free, but the required presence ofan operator on board renders extremely dangerous and nearly impossiblethis solution unless the operator of the mechanical shovel undergoesunlikely performances such as the temporary leaving of the vehicle asthe material drops. Similarly unfeasible results to be the cleaning ofthe slag hole with active electrodes, when considering the high electricpower involved (up to 65 MW).

Therefore the object of the present invention is that of providing anapparatus capable of carrying out the above-mentioned operations, undera remote control and without the presence of an operator on place.

With the pushing machine according to the present invention, during thescrap charge into the furnace a first series of advantages is obtained,among which the most apparent one is that of preventing the scrap fromescaping the slag hole, thus increasing the yield, i.e. the ratiobetween produced steel and charged scrap. Another important advantage inthis stage is that the slag runner, as above defined, is kept free andthe scrap drops entirely within the furnace, not on the thresholdthereof, where it would be lost, thus reducing even more the yield, andwherefrom it should have to be removed with difficulty once solidifyed,with a partial demolition of the threshold itself which then should haveto be restored. Furthermore the completely free slag runner meansimmediate exploitation of the oxygen in the zone where melting occurs,without danger of damaging the lance and anyhow without possiblepresence of scrap between lance and melt bath which would interfere withthe oxygen blow, thus reducing its speed and shielding the temperaturegradient.

Another series of advantages afforded by the pushing machine accordingto the present invention is due to the fact that it can be used forcleaning the slag hole and remaking of the dam at about half casting,when for example the electrodes have delivered a prefixed quantity ofspecific power (such as for example 200 KWh/ton) and are still active.Thus the power delivery is not interrupted and the standstill timebetween two subsequent casts is strongly reduced, while the slagoverflow level is ensured, as the height of the head shield, beingcontrolled to have the fixed values, keeps automatically constant such alevel, thus slag is removed when it is hot, thereby extremely crumbly,without problems of re-building the dam with additional dolomite, allthis occurring without any personal intervention, what would clearlyinvolve some risks.

SUMMARY OF THE INVENTION

Briefly stated, the present invention comprises a pushing machinetravelling on a rail for operating in the slag hole of steel smeltingelectric furnaces. The pushing machine comprises a support frame havinga front zone and a rear zone mounted on a plurality of sliding wheels,at least two of which are driving wheels. A motor is mounted on thesupport frame for driving the at least two driving wheels. An extensiblearm is mounted on said support frame and includes a front shield havinga cross-section slightly smaller than the opening of said slag hole ofthe furnace. Anchoring means are provided for anchoring said supportframe to a fixed location and means for remote control operation offorward and backward movement of the machine, and for separatelyremotely controlling extension and retraction of the extensible arm andthe operation of the anchoring means are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the pushing machineaccording to the present invention will be clearer from the followingdetailed description of a preferred embodiment thereof, given by way ofnon-limiting example, with reference to the annexed drawings in which:

FIG. 1 shows a schematic side view of the pushing machine according tothe invention in two different positions with respect to a smeltingelectric furnace also schematically shown in cross-section;

FIG. 2 shows a top plan view of a preferred embodiment of the pushingmachine of FIG. 1; and

FIG. 3 shows a side view of the pushing machine of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the drawings, the pushing machine according to theinvention essentially comprises a metal frame 1, mounted on four wheels(which could also be of greater number), at least two of which aredriving wheels. In the drawings the rear wheels 2, 2' are assumed to bedriving, whereas the front ones 2a, 2'a are driven. A geared electricmotor 3, having for example a power of about 4 HP, directly actuates,through suitable drive mechanisms, a driving axle 3' at the ends ofwhich there are mounted the wheels 2, 2', thus being able to develope aspeed of about 20 m/min. The electric feeding of the geared motor 3 isaccomplished through an electric cable wound on a reel 13, which issidely mounted on the frame and is designed to automatically release thecable by unwinding the same at approaching the machine to the furnace 10and vice versa re-winding it automatically when the machine is caused tomove backwards.

On the frame 1 there is centrally mounted an extensible arm formed oftwo coaxial tubes 5, 5a, here shown as having a square cross-section,which however could have any different cross-section shape, at the endof the inner one, designated 5a, there is integrally provided a metalhead or shaped shield 6 that forms the actual tool of the apparatus. Thetube 5a of smaller cross-section slides within the outer tube 5 as it isfixed, preferably at its end zone near to the head 6, as better shown inFIG. 3, to a central piston rod of a piston-cylinder 15 having thecylinder fixedly mounted to the outer tube 5 of the extensible arm. Itpreferably shows stiffening ribs 12 spaced along the length and issupported on the frame 1 through a cradle formed of two verticalbrackets or lugs 11, 11' between which a pin 17 is mounted. About pin 17two holed flanges 21 can rotate, which are fixed to the outer tube 5 andconsequently the extensible arm. In a rear side zone of tube 5, itsouter surface is also fixed to the piston rod, preferably having a forkshape 19, of another cylinder 16 which is vertically mounted on theframe 1. Both cylinders are operated by a pressurized fluid means suchas air or preferably oil, in the latter case there being provided ahydraulic system formed of a tank 7 and a pomp-motor unit 4 also fixedlymounted on the frame 1 of the machine and fed by an electric cable,other than that for feeding the geared motor 3. Both cables areindependently wound on the reel 13 and through remote controls (notshown), preferably doubled in a control deck and in an emergencypush-button panel hanging on the sliding floor of the machine, theforward and backward movements or the stop of the machine itself arecontrolled, as well as of forward, backward, upward and downwardmovements of the extensible arm.

Still with reference to FIGS. 2 and 3 there are preferably provided,near the rear wheels 2, 2', anchoring means to the ground, mounted inthe central zone of the frame 1 at a distance therebetween equal toabout the distance between the wheels and formed of two vertical posts 8longitudinally movable with reciprocating movements as being actuated bya driving cylinder 18. The stroke of posts 8 is such as to reachdownwards a position lower than that of contact rail-wheels, thereby theposts can firmly fit into seats formed in the rails themselves or thesurrounding floor so that the pushing machine is anchored during itsoperating manoeuvres, in particular during the forward movement of theextensible arm with shield 6, thus avoiding that by reaction the frame 1can move backward and the push onto the scrap to be kept within thefurnace may fail. The cylinders 18 will be preferably fed through thesame hydraulic system comprising the pump 4 and tank 7 upon controlsthat are also of the remote-type, different from those provided foroperating the extensible arm. This anchoring means can of course showany other different embodiment known in the art.

Finally the pushing machine according to the invention will bepreferably provided with front horizontal studs 9, 9' mounted on bumperplates 23, 23' fixedly mounted onto the frame and positioned before thefront wheels 2a, 2'a to shield them from impacts. The two front studs 9,9' are designed to fit into corresponding holes (not shown) formed inmetal seats, such as rail sections, embedded in the structure 20 orretaining wall placed before the threshold of the slag hole, againstsuch a wall the pushing machine being blocked at the end of its forwardstroke. Thus it is avoided that the machine may undergo a tilting momentduring the operation of cleaning and remaking of the dam or in generalwhen the arm 5, 5a is swinging in the vertical plane.

From the foregoing it is clear the operation of the pushing machineaccording to the present invention, which will be moved forward, withshield 6 completely retracted, until reaching its stroke end where theanti-tilting studs 9 are fitted into the seats of structure 20,whereafter the anchoring posts 8, 8' are lowered and the machine isready for its action through extension of the inner arm 5a to carry thehead shield 6 near the melting bath, thus ensuring that the slag runner10a is kept clear of scrap during the subsequent charge. Possiblemanoeuvres of movement can be carried out also in vertical direction,when it is required to push to the inside of furnace 10 pieces of scrapwhich may assume undesired positions. As the charge is over and meltingis at beginning, the machine can move backward to allow the introductionof the oxygen lance through the runner 10a, for the direct action ofrefining onto the molten product. The lance, whose direction iscontrolled from outside, is not subject to the risks of damages sincethe runner is free and the oxygen, flowing at a speed that can be evensupersonic, is blown in till the inside of the molten bath.

Subsequently, at about half casting, when the electrodes have delivereda prefixed quantity of energy, e.g. 200 KWh/ton, as measured at thecontrol deck the oxygen lance is withdrawn and the pushing machine iscaused to move forward again to perform the cleaning and the damre-building operations, thus ensuring the overflow level of the slagbeing constant. This operation, carried out with subsequent forward andbackward movements of the movable arm, with possible displacement alsoin the vertical plane to augment the mechanical action on the slagitself, occurs easily upon remote control of an operator who is howeverable to observe the working area. It will be noticed that when workingin these conditions, the slag is at high temperature, thereby is crumblyand easily removable from the underlying layer of dolomite or otherrefractory material which does not require demolitions and subsequentre-building. Mention has been already made before about the advantagesin terms of time, of operating in this stage without prolonging thewaiting time between two subsequent casts.

I claim:
 1. A pushing machine travelling on a rail for operating in aslag hole of a steel smelting electric furnace comprising:a supportframe having a front zone and a rear zone mounted on a plurality ofsliding wheels, at least two of which are driving wheels; a motormounted on the support frame for driving said at least two drivingwheels; an extensible arm mounted on said support frame including afront shield having a cross-section slightly smaller than the opening ofsaid slag hole of said furnace; anchoring means for anchoring saidsupport frame to a fixed location, said anchoring means including twoslidable vertical posts mounted to said frame for longitudinal movementin a vertical direction between an upraised, rest position and a loweredposition lower than the level of a contact zone between rail and wheel;and means for remote control operation of forward and backward movementof the pushing machine and for separately remotely controlling extensionand retraction of said extensible arm, and the operation of theanchoring means.
 2. The pushing machine according to claim 1, whereinsaid extensible arm comprises an outer tubular member and at least oneinner tubular member co-axially slidable in a telescopic way andactuated by a piston-cylinder assembly co-axial and fixedly mounted tothe outer tubular member, wherein the shield is attached to the at leastone inner tubular member.
 3. The pushing machine according to claim 2,wherein said outer tubular member is pivotally mounted on the framethrough a pivot which is directed transversely to the extensible arm forallowing vertical movement of the arm about said pivot and furthercomprising a piston-cylinder means for controlling said verticalmovement.
 4. The pushing machine according to claim 2, furthercomprising an oleodynamic system with an oil tank and a motor-pump unitfor pressurizing oil and actuating said piston-cylinder assembly.
 5. Apushing machine according to claim 4, wherein said anchoring meansfurther comprises:a cylinder operated through said oleodynamic systemfor moving the vertical posts, wherein said posts fit into correspondingseats formed on a slide surface of the rails.
 6. The pushing machineaccording to claim 1, further comprising:projections mounted onrespective brackets on the front zone of the frame for protecting theplurality of wheels, wherein the projections are symmetrical withrespect to the extensible arm.
 7. The pushing machine according to claim2, wherein said tubular members (5, 5a) have a square cross-section andthe outer tubular member is stiffened with ribs (12).
 8. The pushingmachine according to claim 1, wherein said motor is electricallyconnected to an electric cable wound on a winding reel mounted on saidframe.
 9. The pushing machine according to claim 3, further comprisingan oleodynamic system with an oil tank and a motor-pump unit forpressurizing oil and actuating said piston-cylinder assembly and saidpiston-cylinder means.
 10. The pushing machine according to claim 2,further comprising:projections mounted on respective brackets on thefront zone of the frame for protecting the plurality of wheels, whereinthe projections are symmetrical with respect to the extensible arm. 11.The pushing machine according to claim 3, further comprising:projectionsmounted on respective brackets on the front zone of the frame forprotecting the plurality of wheels, wherein the projections aresymmetrical with respect to the extensible arm.
 12. The pushing machineaccording to claim 4, further comprising:projections mounted onrespective brackets on the front zone of the frame for protecting theplurality of wheels, wherein the projections are symmetrical withrespect to the extensible arm.
 13. The pushing machine according toclaim 5, further comprising:projections mounted on respective bracketson the front zone of the frame for protecting the plurality of wheels,wherein the projections are symmetrical with respect to the extensiblearm.
 14. The pushing machine according to claim 4, wherein said motorand motor-pump unit (4) are electrically connected to separate electriccables which are wound together on a winding reel mounted on said frame.